1. Field of Invention
The invention relates to a solvent composition that is usable as a lubricant for use for internal combustion engines and the like, or as a coolant for use for fuel cells and the like.
2. Description of Related Art
In recent years, the worldwide emission of carbon dioxide is considered to be causing global warming, and is considered to deteriorate the global environment and adversely affect the human life in the future. The emission of carbon dioxide from the combustion of motor vehicle fuel cannot be ignored. While reduction of the emission of carbon dioxide has been internationally made compulsory on the basis of the Kyoto Protocol, attention is now focused on how to restrain the emission of carbon dioxide without lowering the living standard. As the first step to that end, so-called bioethanol, that is, ethanol produced by the fermentation technology from plant-origin materials, such as corn, sugarcane, used paper, and other plant-origin wastes, has begun to be used as a mixture with a motor vehicle fuel (gasoline) or as a 100% bioethanol motor-vehicle fuel, whereby a new emission of carbon dioxide is avoided and thus the emission of carbon dioxide in the global cycle is lessened. From this time on, the use of bioethanol fuel is an important issue that cannot be evaded in the motor vehicle manufacturing industry.
By the way, various lubricating oils and solvent compositions are used in internal combustion engines of motor vehicles, drive train-system appliances, such as automatic transmissions, shock absorbers, power steering apparatuses and the like, gears, etc., in order to smooth the operation thereof. In order to prevent degradation of a solvent composition that is represented by the foregoing lubricants, fluids and the like, it is known to add an additive, such as oxidation preventative phenol-based additives, amine-based additives, etc. (Japanese Patent Application Publication No. 5-179275 (JP-A-5-179275)). That is, these additives prevent the oxidation by reacting with degraded substances that occur in the solvent composition. However, since insoluble sludge is produced as the lubricant base oil or the like is oxidized by oxygen radicals that occur in the solvent composition, the oxidation preventative agent decreases together with the reaction, and eventually loses its oxidation preventative effect. Besides, since the generation of sludge cannot be completely restrained, functional declination due to production of sludge cannot be avoided. Therefore, according to the related art, effective means for restraining the functional degradation of the solvent composition, such as a lubricating oil and the like, for a long period of time is not known.
In order to solve this problem, a utilization method for the superoxide dismutase enzyme, which is very highly stable against heat, and which is able to essentially enzymatically decompose oxygen radicals that are causative substances that cause oxidative deterioration is proposed (Japanese Patent Application Publication No. 2008-0005797 (JP-A-2008-0005797)).
However, even the solvent composition disclosed in Japanese Patent Application Publication No. 2008-0005797 (JP-A-2008-0005797) cannot easily be used at temperature of 100° C. or higher. Besides, since enzymes are essentially water soluble, the solubility of the enzymes in 100% ethanol and in lubricating oil is low, and the use of enzymes in such solvents is limited.